My 90 GT Conv't has an idle problem. Only when it ain't been cranked up in a while. I have to crank it up and immediately hit the gas pedal or it will die. Is it the idle control sensor?

65

Asked by Dec 26, 2009 at 01:31 PM about the 1990 Ford Mustang GT Convertible

Question type: Maintenance & Repair

I think it has a cam in it, but it started doing this about 3-4 months ago. I have had the car since Feb but had no problem with it.

17 Answers

it could be the sensor, but sinse you mentioned the cam the car may need to be recalibrated or it has missmatch parts on it. check all 3 options out.

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15

if the problem happens when the car sits for a while it may be a few things,first it may just be cold,it may be the Idle air control motor they do get dirty and work very slow or get stuck,or after thecar sits for a while it may bleed off fuel pressure ar the pump may be weak and on initial start after a while it may not have enoght fuel pressure,and with the tap of the gas its just enough time for the p[ressure to build.Try a fuel pressure gauge and see,also try cleaning or changing the IAC motor.

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65

Thanks. I'll try it and see if it works

most likely cause is the idle air control valve, if you have a check engine light it quite possibly the crankshaft position sensor

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65

I appreciate the info. The check engine light is not on, so I will have the valve checked. Thanks

35

if you let it sit for awhile prime the fuel pump, just turn the ignition to on but dont try to start wait like 5 seconds turn the iginition off do this a few time to prime the fuel line.when it sits the fuel pressure bleeds off so u need to get it up to pressure before starting it. Im guessing its not carbed so it wont really do anything to hit the gas when its turning over. deff clean the throttle body mayby put some injector clearner in on your next trip to the gas station.

65

I definitely appreciate that info Chris. I did not think about priming the fuel lines. Thanks again.

5

try cleaning your maf sensor. once they get dirty the computer gets a false reading and doesnt know how much air and fuel to mix together. mass air flow is far superior to a speed density unit but requires maitnence

5

mite b air in ur fuel lines... does it get bak to idling normally after a wile? or does this continue?

65

After it warms up, its good. It takes at least a minute of constant revving to hold an idle.

5

ok doesnt sound like da fuel lines... check ur pressure release valve... im not sure i old cars hav them but what they do is help da engine heat up by holding the water in there and not allowing it to flow around, the water gets hot quick and helps the engine heat up much faster... if that is the problem it is quite a big one... it wont b now but it could evolve into sumfing big because in a cold engine the pistons shrink and they start to rattle around the piston chamber weakening the engine...

5

ok doesnt sound like da fuel lines... check ur thermostat... im not sure i old cars hav them but what they do is help da engine heat up by holding the water in there and not allowing it to flow around, the water gets hot quick and helps the engine heat up much faster... if that is the problem it is quite a big one... it wont b now but it could evolve into sumfing big because in a cold engine the pistons shrink and they start to rattle around the piston chamber weakening the engine... sry... this was wat i meant to say... dunno y i said pressure release vavle before... my bad...

5

hahah you think pistons SHRINK in a cold engine? oh boy. if they shrunk and rattled around in their sleeves then nobodys engine would last say two months through winter. a solid metal composite is made at an exact size and kept that way. and wayne sounds to me like you MIGHT have a leak in your fuel rail's schrade valve. the little screwtop that looks like it should be on your tire but in fact bleeds fuel instead of air. turn your car to ignition but dont start it and do NOT touch the gas pedal. repeat three or four times then screw off the schrade valve top and depress the metal insert to release the mixture of remaining air and new fuel from the line. then prime the lines once and try it again. this should reset the MAF sensor then clear for take off. if that doesnt do the trick, i have noticed nobody has said check your plugs. always a good start.

5

u probably r rite and u probably do no more dan me but i hav had dat experience with my mates car with da termostat not working and thats wat i learnt at school... im just passing on wat i hav learnt

Wouldnt think of the plugs, since that computer is designed to detect misfires and register a check engine light, as would any problems with the MAF sensor (typically it'd trigger check engine lights for oxygen sensors on both exhaust banks at the same time..a manifold vacuum leak has the same symptoms too)

95

Idle air controls get dirty. When they do they idle bad or not at all. You need to pull off the air inlet tube to IAC, remove it and clean IAC with a rag and throttle body cleaner. Spray rag and wipe, do not spray in throttle body. You may want to also remove TB and clean that. Cost is just TB cleaner and new gaskets.

55

try the throtle position sensor and the fuel pump it has a one way check valve in the pump that keeps the fuel in the lines when the pump is off u can check this by hooking up a pressure guage to the schrader vavle on the fuel rail just turn on the key and let the pump prime u should have pressure right away and it should build up to no less than 35psi..and make sure the vacuum line is on ur pressure regulator located on fuel rail

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